Early caries detection methods according to the depth of the lesion: An in vitro comparison

Abstract

Purpose: The aims of this study were to estimate the histological and optical changes of early carious lesions according to the duration of demineralization and to compare the efficacy to detect early carious lesions of a quantitative light-induced fluorescence (QLF) system with a spectrophotometer according to the lesion depth. Methods: Eighty-four bovine enamel specimens were immersed in demineralizing gel for six distinct days. The severities of lesions were evaluated by lesion depths (Ld) by polarized light microscopy, fluorescence loss (Delta F) using QLF, and brightness (Delta L*) by spectrophotometry. The relationships between Ld, Delta F, and Delta L* were analyzed. Results and conclusion: Ld tended to be significantly deeper according to the demineralizing period (p < 0.05). The Delta F significantly decreased (p < 0.05) and the Delta L* significantly increased with increasing the demineralizing period (p < 0.05). More shallow lesions (Ld <= 200 mu m) showed a strong relationship between Delta F and Ld (r = -0.898, p < 0.001), while there was a strong relationship between Delta L* and Ld in deeper lesions (Ld > 200 mu m) (r = 0.858, p < 0.001). Our findings show that QLF system is a more efficient device for shallow early caries detection and that the spectrophotometer is a more stable device for the detection of deeper lesions.